1. Field of the Invention
The present invention relates to a technique for writing data onto a disk of a hard disk drive.
2. Background Information
Hard disk drives contain a plurality of magnetic heads that are coupled to rotating disks. The heads can magnetize and sense the magnetic fields of the disks to write and read data, respectively. The heads are coupled to a pivoting actuator arm that has a voice coil motor.
Data is typically stored on tracks that extend radially across the disk surfaces. The voice coil motor can be energized to pivot the actuator arm and move the heads to different track locations. Each track is typically divided into a number of sectors. Each sector contains at least one data field.
It is generally desirable to increase the storage capacity of a hard disk drive. Storage can be increased by reducing the width of each track. As shown in FIG. 1. the width of a track 1 may be less than the width of a head 2. When the head writes onto a target track it may also write onto adjacent tracks, corrupting the data on those tracks. To prevent adjacent track corruption the data from the adjacent tracks are moved to another location before writing onto the target track. The data is then restored for the adjacent track. Restoring data onto the adjacent track requires another cycle of moving and restoring data for the next adjacent track. The disk may include fixed guard bands to terminate the process of moving and restoring data on adjacent tracks. The guard bands contain no data. The process of moving the data from adjacent tracks and then writing data onto a target track is repeated until the head reaches the guard band. Because the guard band does not contain valid data there is no need to move data before writing to the target track. The guard bands are typically located every hundred tracks on the disk. The process of moving and then restoring adjacent tracks can be an inefficient way to write data, particularly when writing random data that may only require a few tracks. For example, writing to a track in the center of a data region requires the continued process of moving and restoring adjacent tracks until the head reaches a guard band.